High-dynamic-range video

High-dynamic-range video (HDR video) describes high dynamic range (HDR) video that is greater than standard dynamic range (SDR) video which uses a conventional gamma curve. SDR video when using a conventional gamma curve and a bit depth of 8-bits per sample has a dynamic range of about 6 stops (64:1). When HDR content is displayed on a 2,000 cd/m2 display with a bit depth of 10-bits per sample it has a dynamic range of 200,000:1 or 17.6 stops.

In February and April 1990, Georges Cornuéjols introduced the first real-time HDR camera combining two successively or simultaneously captured images.

In 1991 the first commercial video camera using consumer-grade sensors and cameras was introduced that performed real time capturing of multiple images with different exposures, and producing an HDR video image, by Hymatom, licensee of Georges Cornuéjols.

Also in 1991, Georges Cornuéjols introduced the principle of non linear image accumulation HDR+ to increase the camera sensitivity: in low-light environments, several successive images are accumulated, increasing the signal to noise ratio.

Later, in the early 2000s, several scholarly research efforts used consumer-grade sensors and cameras. A few companies such as RED and Arri have been developing digital sensors capable of a higher dynamic range. RED EPIC-X can capture time-sequential HDRx images with a user selectable 1–3 stops of additional highlight latitude in the "x" channel. The "x" channel can be merged with the normal channel in post production software. The Arri Alexa camera uses a dual gain architecture to generate an HDR image from two exposures captured at the same time.

With the advent of low-cost consumer digital cameras, many amateurs began posting tone mapped HDR time-lapse videos on the Internet, essentially a sequence of still photographs in quick succession. In 2010 the independent studio Soviet Montage produced an example of HDR video from disparately exposed video streams using a beam splitter and consumer grade HD video cameras. Similar methods have been described in the academic literature in 2001 and 2007.

Modern movies have often been filmed with cameras featuring a higher dynamic range, and legacy movies can be upgraded even if manual intervention would be needed for some frames (as when old black-and-white films are upgraded to color). Also, special effects, especially those in which real and synthetic footage are seamlessly mixed, require both HDR shooting and rendering. HDR video is also needed in applications that demand high accuracy for capturing temporal aspects of changes in the scene. This is important in monitoring of some industrial processes such as welding, in predictive driver assistance systems in automotive industry, in surveillance video systems, and other applications. HDR video can be also considered to speed image acquisition in applications that need a large number of static HDR images are, for example in image-based methods in computer graphics.

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